It is a difficult and taxing task to manually steer a multiple row harvesting machine even when the machine is moving along the rows at a modest rate of speed. The row crop separators which guide the crop to the cutting elements of the machine are often obscured by dust, crop material and/or vegetation such that precise manual steering by visual observation is difficult if not impossible. To alleviate this problem, steering control systems have been developed which employ mechanical feelers to determine the position of a standing row crop relative to the row crop separators. While steering control systems with mechanical feelers offer an improvement over guidance by visual observation, these systems have certain disadvantages in that the mechanical feelers are subject to fouling and damage. In addition, because of the environment in which the feelers must operate, they must be serviced frequently to insure that they are mechanically free.